While the advantages of employing a load stabilizer or box clamp assembly on a forklift truck to clamp, secure or stabilize a load carried by the tines or forks of the truck are well known, there remains a substantial disadvantage which has limited use of such stabilizer assemblies to applications in which they are absolutely essential, namely, the inability to compactly store the clamp assembly while mounted to the forklift. Thus, the safety advantages which would accrue from use of a load stabilizer are often short-cut because of the impossibility or awkwardness of storing the stabilizing unit when not in use.
Most forklift load stabilizers include a horizontally extending arm which acts as a clamp and is reciprocally mounted to a frame immediately in advance of the forklift mast. The arm is driven by hydraulic means, such as a hydraulic cylinder, so that it may be selectively brought into engagement with the load carried by the truck so as to stabilize the same in combination with the forklift tines. Typical forklift load stabilizers or box clamps are shown in my prior U.S. Pat. No. 4,136,793 and the prior art cited in that patent.
In my U.S. Pat. No. 4,136,793 a load stabilizer assembly is provided which can be moved to a stored position in which it is not superimposed over the tines of the forklift. Thus, the assembly is formed so that it can be pivoted about vertical axes to a position over the body of the forklift truck to permit towing of the truck. While this ability to store the stabilizer or box clamp has been found to have substantial advantages, it is not designed to permit storage of the box clamp in a position which enables active use of the forklift for tasks that do not require the stabilizer.
While most load stabilizers or box clamp assemblies include horizontal arms which are rigidly fixed with respect to the vertical framework or carriage upon which they reciprocate, U.S. Pat. No. 3,272,364 discloses a clamp structure for a forklift which is pivotally mounted so as to provide two positions for carrying cartons. This specialized clamp structure of this forklift, however, extends only a very short distance outwardly of the forklift mast because it is designed for use with relatively short forks of the type employed to carry boxes or drums. A similar short-fork structure is shown in U.S. Pat. No. 2,807,382. The clamp mechanisms in these patents, however, are not similar to the load stabilizer or box clamp mechanisms which extend a substantial distance from the forklift and thereby present a much more substantial storage problem when not in use.
Typical of the relatively large clamp structures to which the present invention is directed are the structures in U.S. Pat. Nos. 2,684,165, 2,875,912, 3,024,929, 3,133,655, and 3,567,053.